Mungbeans are one of the important agricultural products for food security in East Nusa Tenggara (NTT) Province, which is one of the driest regions in Indonesia. The low productivity and profitability of mungbean farming in this region are caused by factors that influence agricultural inefficiency. This study was conducted to measure the productivity and technical efficiency levels, as well as investigate the factors affecting farm inefficiency, using the Technical Efficiency Effect Model (TEEM) applied to the frontier logarithmic transcendental production function. The method applied in this research is descriptive qualitative based on survey and interview results through primary and secondary data. Firstly, the results showed that mungbean farming was in the increasing return to scale stage of production and productivity only reached 57% of its production potential, with a technical efficiency level of 66%. Secondly, the factors that positively influence the low productivity and technical efficiency level of mungbean farming are land, seeds, labor, and the interaction between land and labor. Meanwhile, farmer experience and farm training significantly reduce the inefficiency of mungbean farming. It is suggested that increasing land productivity with appropriate and intensive modern technology and improving labor skills are the main strategies for reducing inefficiencies and increasing the income of smallholder farmers in drylands.